The present invention relates generally to the reduction of contaminants emitted into the atmosphere as a result of commercial and industrial processes and pertains, more specifically, to apparatus and method for the removal of contaminants from commercial and industrial exhausts.
The continuing pursuit of more stringent regulations pertaining to the control of contaminants emitted into the ambient atmosphere has led to the requirement for more effective treatment of emissions emanating from commercial and industrial processes. In particular, the removal of toxic substances from commercial and industrial exhausts has received increased attention. Electrostatic precipitators have found widespread use in the treatment of contaminated exhaust gases. Efforts to increase the effectiveness of electrostatic precipitators have included the use of various arrangements in which liquids or gases are introduced into the exhaust gases as the exhaust gases are passed through electrostatic fields established in these electrostatic precipitators for further reducing the concentration of contaminants in the exhaust gases. It has been suggested that exhaust gases can be treated to remove even very low concentrations of certain contaminants by generating ions of selected reagent gases and injecting these ions into the contaminated industrial exhaust gases to produce reactions with the particular contaminants to be removed. The reagent gas is selected to produce ions which, in turn, will react with particular contaminants to assist in removal of these contaminants from the exhaust gases. More recently, nozzle gas injectors utilizing a corona discharge have been proposed for generating radicals to be injected into combustion gases being treated for removal of nitrogen oxides from the combustion gases.
The present invention provides an improvement which accomplishes a more simplified and practical generation, injection and distribution of ions and other chemically active species produced by selected reagent fluids into currently available electrostatic precipitator configurations for enhancing the ability of otherwise essentially conventional electrostatic precipitators so as to enable the removal of contaminants heretofore difficult, if not impossible, to remove from commercial and industrial exhausts. As such, the present invention attains several objects and advantages, some of which are summarized as follows: Combines the ability of an electrostatic precipitator to remove particulates with the added ability to remove further noxious substances in a single apparatus; enables effective and efficient removal of a wider range of unwanted substances from commercial and industrial exhaust gases through the use of reactions heretofore unavailable in a single electrostatic precipitator; provides an effective method for introducing and distributing reactive ions and other chemically active species into a stream of contaminant-laden gas for the removal of a wider variety of contaminants in a single apparatus; enables the removal of contaminants heretofore difficult, if not impossible, to remove in conventional electrostatic precipitators; effects the conversion of removed contaminants into environmentally benign forms and produces minimal to no undesirable byproducts; facilitates the handling and disposition of a wider range of contaminants removed from industrial exhaust gases; allows the use of currently available electrostatic precipitator designs, configurations and technology with minimal modification to adapt to the added ability to remove noxious substances heretofore not capable of effective removal in a single apparatus; reduces installation space requirements and cost; exhibits exemplary performance over an extended service life.
The above objects and advantages, as well as further objects and advantages, are attained by the present invention which may be described briefly as an improvement in an electrostatic precipitator for removing contaminants from a stream of contaminant-laden gas conducted through a conduit in the electrostatic precipitator, the electrostatic precipitator including a longitudinally-extending discharge electrode placed within the conduit, and a collector electrode spaced laterally from the discharge electrode for establishing an electrostatic field between the discharge electrode and the collector electrode in response to a prescribed electrical potential between the discharge electrode and the collector electrode, the improvement comprising: a manifold passage extending longitudinally within the discharge electrode; a plurality of electrode elements located along the discharge electrode and projecting laterally from the discharge electrode into the conduit and toward the collector electrode, each electrode element terminating in at least one sharp-edged tip located within the conduit and spaced laterally from the collector electrode for establishing a corona discharge active zone juxtaposed with the tip in response to the prescribed electrical potential; an injector passage extending laterally through the discharge electrode at each electrode element, each injector passage communicating with the manifold passage and juxtaposed with the tip of a corresponding electrode element; and a source of reagent fluid communicating with the manifold passage for distributing reagent fluid through each injector passage toward each tip such that reagent fluid will pass through the corona discharge active zone juxtaposed with each tip for activating the reagent fluid as the reagent fluid is injected into the stream of contaminant-laden gas.
In addition, the present invention includes an improvement in a method for removing contaminants from a stream of contaminant-laden gas conducted through a conduit in an electrostatic precipitator, the electrostatic precipitator including a longitudinally-extending discharge electrode placed within the conduit, a collector electrode spaced laterally from the discharge electrode for establishing an electrostatic field between the discharge electrode and the collector electrode in response to a prescribed electrical potential between the discharge electrode and the collector electrode, the improvement comprising: providing a manifold passage within the discharge electrode; providing a plurality of electrode elements located along the discharge electrode and projecting into the conduit and toward the collector electrode, each electrode element terminating in at least one sharp-edged tip located within the conduit and spaced laterally from the collector electrode; establishing a corona discharge active zone juxtaposed with each tip in response to the prescribed electrical potential; providing an injector passage extending through the discharge electrode at each electrode element, each injector passage communicating with the manifold passage and juxtaposed with the tip of a corresponding electrode element; and distributing a reagent fluid through each injector passage toward each discharge tip such that reagent fluid will pass through the corona discharge active zone juxtaposed with each discharge tip to activate the reagent fluid as the reagent fluid is injected into the stream of contaminant-laden gas.
The invention will be understood more fully, while still further objects and advantages will become apparent, in the following detailed description of preferred embodiments of the invention illustrated in the accompanying drawing, in which:
FIG. 1 is a partially diagrammatic, longitudinal cross-sectional view of an apparatus constructed and operated in accordance with the present invention;
FIG. 2 is an enlarged lateral cross-sectional view taken along line 2xe2x80x942 of FIG. 1;
FIG. 3 is a cross-sectional view taken along line 3xe2x80x943 of FIG. 2;
FIG. 4 is an end view taken as indicated by line 4xe2x80x944 in FIG. 3;
FIG. 5 is a fragmentary cross-sectional view similar to FIG. 3, and illustrating another embodiment of the invention;
FIG. 6 is an end view taken as indicated by line 6xe2x80x946 in FIG. 5; and
FIG. 7 is a partially diagrammatic pictorial perspective view of another apparatus constructed and operated in accordance with the present invention.